DISCUSSION (Adapted from the investigator's application): A change in voltage across the plasma membrane represents the fundamental neural signal. Active propagation of this signal, and its coupling to synaptic transmission, depends on a superfamily of ion channels which open their conduction pathway in response to changes in membrane voltage. How a voltage change causes conformational rearrangements in these channels that open them is not understood. To address this question, the investigators have developed a novel method that reports conformational changes in real-time. This method uses fluorescent thiol reagents to tag cysteine-substituted channels in a site-specific manner, and combines measurement of fluorescent emission with voltage-clamping. In this way they can identify the gating transitions that correlate with the movement of the tagged protein segment. The investigators propose to use this and other methods to identify the structural components of gating in the voltage-gated Shaker potassium channel. They outline a plan for determining how gating elements interact, within and between subunits, and ask how such interactions act to stabilize gating conformations, to couple voltage-sensing to gating, and to confer cooperativity on certain conformational rearrangements. Abnormal function of members of the voltage-gated channel superfamily has been implicated in a variety of human diseases. Information obtained in the proposed project will help to elucidate the structural basis of gating for the entire superfamily of channels. This information will be valuable for the design of specific chemical and gene therapies to treat diseases which are caused by channel defects, or which are arneliorated by modulation of specific channel types.